1. Field of the Invention
The present invention relates to a method for producing continuously drain pipes, flexible drain pipes, suction hoses and the like made of synthetic resins and apparatus therefor.
2. Description of the Prior Art
Methods for producing flexible pipes (spiral pipes) with a rib are disclosed in Japanese Patent Publication Nos. 17987/1976 and 17988/1976. These patents disclose a method which comprises spirally shearing a hard resin pipe extruded into a pipe shape as desired by a rotating cutter, and integrally forming a spiral rib on the outer peripheral surface of a tubular member.
Alternatively, Japanese Patent Publication No. 53179/ 1982 provides a method comprising feeding a tape with a rib, while extruding the same, to an outside of an inclined winding shaft arranged at right angles to the extruding direction, rotating the winding shaft, and winding and fusing said tape with a rib to produce a spiral pipe.
The former method, i.e., the method for shearing a part of a pipe extruded by rotation of a cutter has disadvantages that a spiral rib is solid and is square in sectional shape, and as a result, a sectional shape of the rib cannot be suitably selected, and the sheared section is square-like and in addition, a large diameter pipe is heavy.
The latter method, i.e., the method for winding a tape with a rib which comprises winding a rib material extruded toward the outer peripheral surface of a rotating winding shaft as the latter rotates to produce a pipe, and therefore, this method has advantages that pipes can be produced without requiring excessive efforts and accurately whereas the aforesaid method has disadvantages that the apparatus becomes large-sized, has a problem in that a part of a tape is superposed and wound to have a tubular shape, which is liable to peel, and involves a problem in that since the product is rotating, apparatuses for winding, cutting and the like carried out in the succeeding steps become inevitably complicated and large-sized, thus increasing cost.